Hypervelocity pellet projector



Aug. 23, 1966 A. B. MERENDINO ETAL HYPERVELOGITY PELLET PROJECTOR FiledMay 14, 1964 INVENTOFS 456 15, Merpna'zno Joseph M. Reg n SeymourKronman.

United States Patent 3,267,853 HYPERVELOCITY PELLET PROJECTOR Alfred B.Merendino, Baltimore, and Joseph M. Regan and Seymour Kronman, Aberdeen,Md., assignors to the United States of America as represented by theSecretary of the Army Filed May 14,, 1964, Ser. No. 367,603 5 Claims.(Cl. 102-24) The invention described herein may be manufactured and usedby or for the Government for governmental purposes, without the paymentto us of any royalty thereon.

This invention relates to a device designed to produce pellets ofvarying size, velocity and materials to simulate meteoritic impact onballistic missiles and/or orbiting satellites so that the effects may beobserved and measured in the laboratory.

These pellets are produced by utilizing a hollow shaped charge and somodifying the construction that the net prodnot will be a single pelletrather than the customary elongated jet.

A shaped charge is an explosive device having usually a cone-shapedcavity within the explosive charge and the base of the cavity being openand facing the intended direction of the charge. -The cavity of thecharge is usually provided with a thin liner of metal or othernonexplosive material which is designed to more effectively concentratethe explosive energy in a jet and thereby increase the penetratingeffect. When the explosive is detonated at the end opposite the cavity,the lining collapses to form a high speed jet with the forward portionsmoving at extremely high velocities. Depending on the geometrical shapeof the liner and the material of the liner as well as the explosiveemployed, velocities exceeding 40,000 feet per second may be achieved.Heretofore, the high velocity jet of such shaped charges have beenutilized to obtain greater penetration of steel armor and in perforatingoil, gas and water wells.

In the discharge of a shape-d charge, it is noted that the initial jetor the tip is formed by the region near the apex of the cavity liner andthe subsequent parts of the jet are made up of the remainder of thecollapsed liner. This action suggests that if the remainder of the linercan be separated or diverted either when forming a jet or interruptedafter the jet has formed, the tip will be isolated as a discreet pellet.

It is therefore the object of this invention to so modify a shapedcharge that its output will be a single pellet rather than an elongatedjet.

This modification is accomplished by placing within the cavity at thebase a Lucite inhibitor which substantially closes the cavity with theexception of an opening provided in the center of the inhibitor. Thisinhibitor, so constructed and properly positioned, is operative inisolating the tip from all but a small portion of the low velocitytrailing material. This trailing material consists of slug from thecollapsed liner, partially collapsed liner and uncollapse'd liner and isdeflected laterally with a semicircular peripheral charge placed on theoutside around the shaped charge at the base of the conical cavity.

It is a further object of this invention to utilize this pelletprojector as a means of simulating the movement of meteoritic bodies athigh velocities and to study the impact of such bodies.

Other objects and advantages will become more apparent from thefollowing description of the drawing which illustrates the principle ofthis invention.

In the drawing:

FIGURE 1 is a diagrammatical vertical section of the shaped charge ofthis invention, and

FIGURE 2 is a top plan view of the device shown in FIGURE 1.

Patented August 23, 1966 Referring to the drawing, 10 represents acylindrical shaped charge having a cone-shaped cavity 11 therein. Thewalls of the conical cavity 11 are lined with a liner 12 of a ductilemetal such as aluminum and the base or mouth 13 of the liner 1 2 has aperipheral flange 14 which is integral with and of the same material asthe liner 12. A small brass cylindrical cap 15 is used to seal the topof the liner 12 if the explosive 10 is formed by casting. At the base ofthe cavity a Lucite inhibitor 16 is fitted securely by any convenientmeans within the mouth 13 of the liner 12, flush with the flange 14 andsubstantially closing the mouth 13. The inhibitor 16 is provided with anopening 17 for the purpose of limiting the discharge to that portion ofthe collapsed liner that is free to escape through said opening. It hasalso been ascertained that the height of the opening 17 or the inhibitor16 has a definite relation with the length of the pellet ejected, i.e.an increased height produces a shorter pellet. To insure that only asingle pellet will be ejected, it is necessary to deflect any trailingmaterial and this is accomplished by a semicircular deflector charge 18placed around the charge on the outside and resting on the flange 14.The deflector charge 18 is made semicircular so that when discharged,trailing material will be directed in a direction other than the pellet.

In operation, the hollow shaped charge 10 is ignited and on dischargethe conical liner 12 tends to follow the customary collapse until itreaches the inhibitor 16 which prevents anything from passing exceptthat portion of the liner that passes through the opening 17 and whichemerges as a single pellet. The isolation of the single pellet is made acertainty by the semicircular deflector charge 18 detonating whenignited by the shaped charge adjacent the base of the conical cavity 1'1and discharging in a direction other than the directed shaped charge aspreviously explained in detail.

This pellet project-or provides a valuable research tool to study thephenomenon of ultra high velocity (meteoritic) impact. With the adventof ballistic missiles and orbiting satellites, the need of understandingthe physics of the impact at these velocities has become paramount.Satellites can be expected to encounter meteorites ranging in size frommicroscopic particles to pieces weighing in the order of hundreds ofgrams. Obviously, to study the impact of such particle sizes, these highvelocities must be achieved on earth where sophisticated instruments canmeasure energy and momentum, and the materials or bodies subjected tothese simulated impacts are available for examination.

If the shape charge has a cavity with an angle of 37 as shown in thedrawing, a base of 3.4 inches, with an opening in the Lucite inhibit-orof 1.0 inch, a semicircular deflector charge 1.0 inch square in crosssections, the pellet ejected will weigh approximately 5.0 grams and thevelocity will be 9.6 kilometers per second or 31,000 feet per second.

Two principles of a shaped charge are emphasized as fundamental. First,as the size of the charge is scaled the mass of the jet producedincreases as the cube of the scale factor. That is to say, if the chargeabove described were doubled in diameter the mass of the pellet would beincreased by a factor of 8 and the pellet will weigh about 40 grams. Ittherefore may easily be calculated that a projector 12 to 14 inches indiameter will produce a pellet weighing approximately 300 grams. Suchscaling does not change the velocity and the 300 gram pellet will alsohave a velocity of 31,000 feet per second. The second principle, thevelocity of the jet tip or pellet increases as the included angle of theliner is reduced until a limit is reached in which the jet tip istravelling at twice the rate of detonation of the explosive used. Forexample, the charge employed with a rate of detonation of 7800 metersper second will move the pellet more than 40,000 feet per I I second ifthe angle is nominally 20. Theoperative range of'angle at the apex ofthe cavity is from 20 to 60.

This device employing the inhibited jet charge design is' y anextremelyuseful and economical device for studying the 'elfects ofhypervelocity impacts on various targets by its capability of simulatingmeteoritic velocities.

Whilethis inventionhasbeen illustratedas one specific embodiment, itmaybe used advantageously in other endeavors and should only be limitedby the appended claims.

' What is claimed is:

1. An apparatus for converting a collapsed shaped I charge liner to asingle pellet comprising a conical hollow shaped charge withthe baseopen, a metal liner for said shaped charge, an inhibitor secured withinsaid open base and substantially closing same, said inhibitor providedwithv a. small opening in the center and means attached at the base forlimiting the output of said inhibitorto a single pellet.

I 2.'An' apparatus for producing a single pellet from a shaped chargeliner comprising, 'a conical hollow shaped charge With the base open,ametal line-r for said shaped charge, an inhibitor secured withinsaidopen base and substantially closing same, a semicircular deflectorcharge on the outside ofthe shaped charge at the base to force anyscattered material following the collapsed lincrin a direction otherthan that of the pellet, said inhibitorfl provided with a small openingin the center which upon discharge of the shaped charge limits thecollapsed liner to the passage of a single pellet therethrough I I I I I3. An apparatus for producing a single pellet from a shaped charge linercomprising a conical hollow shaped charge having a cylindrical tip atthe apex and the base open, the angle at the apex varying from 20 to 60with the smaller angle: producing the highest velocityon :dis-:

charge, a metal liner for said shaped charge andcylindrical tip,- afrusto-conical inhibitor securely fitted Within the open base of theshaped charge and substantially closing I 4.; A shaped chargedesigned tofire a, single pellet com-i prising a conical hollow shaped charge withthe b se, open, I

a metal liner for the hollow charge adapted to collapse in the form of ajet on discharge, a frusto-conical inhibitor to con-fine said jetsecured within the open baseand substantially closing same, asemicircular deflector charge fitting the outside of the baseoi theshaped charge todirect any following material in a direction other than,that of the charge,said inhibitorhaving an opening in the center for thepassage of a portion of the collapsed liner, said portion emerging fromthe opening as a single pellet, the

length of the pellet increasing with the decreasing depth of the openingand the velocity increasing by decreasing the angle at the apex of thehollow cone. 5. A; shaped charge designed to fire a single pelletcomprising a conicalhollow shaped charge with the base open,

2. metal liner for the hollow charge adapted tocollapse in the formofajet on discharge, a frusto-conical inhibitor to confine said jetsecuredwithin the open base and sub-- stantially closing same, asemicircular deflector charge fitting the outside ofthe base of theshaped charge to direct any following materialin a direction other thanthat of.

the charge, said inhibitor having an opening in the center forthepassage of a portion of the collapsed liner, said portion emerging fromthe opening asaisingle pellet, the

mass of the pel'lct'increasingasthe size, of the charge is I Iincreasedwith thevelocity remaining the same regardless of'the change inmass.

, p a a a References Cited by the Examiner UNITED STATES PATENTS t t t2,649,046 8/1953 Davis 10224 2,765,739 10/1956 Mohaupt et al. 1022OFOREIGN: PATENTS 837,900 6/1960 Great Britain.

341,743, 11/1959 Switzerland.

OTHER REFERENCES I Pugh et allz Theory of Jet FormationbyCharges WithLined Conical Cavities, Journal of Applied Physics, vol. 23, No. 5, pp.532-536.

BENJAMIN A. BOROHELT, Primary Examiner.

R. V. LOTTMANN, V. R. PENDEGRASS,

Assistant Examiners.

1. AN APPARATUS FOR CONVERTING A COLLAPSED SHAPED CHARGE LINER TO A SINGLE PELLET COMPRISING A CONICAL HOLLOW SHAPED CHARGE WITH THE BASE OPEN, A METAL LINER FOR SAID SHAPED CHARGE, AN INHIBITOR SECURED WITHIN SAID OPEN BASE AND SUBSTANTIALLY CLOSING SAME, SAID INHIBITOR PROVIDED WITH A SMALL OPENING IN THE CENTER AND MEANS ATTACHED AT THE BASE FOR LIMITING THE OUTPUT OF SAID INHIBITOR TO A SINGLE PELLET. 